The present invention relates to a coil winding machine suitably used to wind a conducting wire of a deflection coil on a coil bobbin in a saddle type and a method of producing a deflection coil by using the coil winding machine.
In color cathode ray tubes (hereinafter, referred to as xe2x80x9ccolor CRTsxe2x80x9d), three electron beams emitted from an electron gun are deflected in the vertical and horizontal directions to display a color image on a screen.
A deflection yoke having a horizontal deflection coil and a vertical deflection coil is used for deflecting electron beams.
The deflection yoke is mounted on a cone portion extending from a neck portion and a funnel portion of a CRT.
The deflection yoke forms a deflection magnetic field by making a horizontal deflection current flow in the horizontal deflection coil and also making a vertical deflection current flow in the vertical deflection coil, to deflect electron beams in the vertical and horizontal directions by the deflection magnetic field.
The three electron beams thus deflected are converged at one point of a color selection electrode (aperture grill or shadow mask), thereby to reproduce a desired color image on the screen.
By the way, in recent years, there have been strong demands toward higher accuracy of TV sets, computer displays, and the like.
In particular, to realize the enlargement of a display screen for TV sets and also realize the display of high-definition images for computer displays, the deflection frequency of electron beams has become increasingly higher.
Further, to reduce distortion and unnecessary reflection from the exterior at a peripheral portion of the screen of a CRT, flattening of the panel of the CRT has been developed.
A CRT having a flattened panel (hereinafter, referred to as xe2x80x9cflat panel CRTxe2x80x9d), however, has an inconvenience that since the distance between a deflection yoke and each of the right and left ends becomes longer, it becomes very difficult to ensure the convergence of electron beams in combination of reduction in raster distortion only by a deflection distribution generated by the deflection yoke.
At present, TV sets and computer displays using flat panel CRTs have been commercially available.
In such a flat panel CRT, however, if the convergence of electron beams in combination of reduction in raster distortion cannot be obtained only by a deflection magnetic field generated by a deflection yoke, it must be realized by using a complicated correction circuit or performing difficult adjustments.
On the other hand, from the viewpoint of electric characteristic, as the number of turns of a conducting wire of a deflection coil becomes larger, it becomes harder for a current with a high frequency to flow in the conducting wire.
Accordingly, to increase a deflection frequency of electron beams, it is required to reduce the number of turns of a conducting wire of a deflection coil.
The reduction in the number of turns of a conducting wire means that the field strength per one turn of the conducting wire becomes large to raise the sensitivity.
As a result, a deviation in winding position of a conducting wire exerts a large effect on the deflection magnetic field distribution of a deflection coil.
For this reason, as the deflection frequency of electron beams becomes, it is strongly required to make higher the accuracy of a winding distribution of a deflection coil higher.
FIGS. 1A to 1H are schematic views showing a coil winding procedure for producing a saddle type deflection coil by using a related art coil winding machine.
First, as shown in FIG. 1A, a nozzle 52 placed inside a coil bobbin 51 is moved up along the inner peripheral surface of the coil bobbin 51 while feeding out a conducting wire W.
As shown in FIG. 1B, at a position near an opening of the nozzle 52, which has been moved above the coil bobbin 51, an upper hook 53 is turned into a xe2x80x9cclosexe2x80x9d position to catch the conducting wire W by the tip of the hook 53.
The hook 53 is then moved outside the coil bobbin 51 while the conducting wire W is fed out of the nozzle 52.
As shown in FIG. 1C, the coil bobbin 51 is rotated, to wind the conducting wire W in a circumferential guide groove (not shown) of the coil bobbin 51.
When the winding angle of the conducting wire W reaches a specific angle, the rotation of the coil bobbin 51 is stopped, and, in this state, the hook 53 is turned into an xe2x80x9copenxe2x80x9d position to release the conducting wire W from the tip of the hook 53.
As shown in FIG. 1D, inside the coil bobbin 51, the nozzle 52 is moved down along the inner peripheral surface of the coil bobbin 51 while feeding out the conducting wire W.
As shown in FIG. 1E, at a position near the opening of the nozzle 52, a lower hook 54 is turned into the close position to catch the conducting wire W by the tip of the hook 54.
As shown in FIG. 1F, the hook 54 is moved outside the coil bobbin 51 while the conducting wire W is fed out of the nozzle 52.
Then, as shown in FIG. 1G, the coil bobbin 51 is rotated in the direction reversed to the rotational direction at the step shown in FIG. 1C, to wind the conducting wire W in the circumferential guide groove (not shown) of the bobbin 51.
When the winding angle of the conducting wire W reaches a specific angle, the rotation of the coil bobbin 51 is stopped.
In such a state, the hook 54 is turned into the open position to release the conducting wire W from the tip of the hook 54.
The conducting wire W has been thus wound by one turn.
Next, the nozzle 52 is moved up again, as shown in FIG. 1H. After that, the above-described operation is repeated while the winding position of the conducting wire W on the inner peripheral side of the coil bobbin 51 is sequentially shifted in the circumferential direction of the coil bobbin 51.
In this way, the conducting wire W for a deflection coil is wound around the coil bobbin 51 in a saddle type.
The above-described related art coil winding machine performs, as shown in FIG. 2, the operation of catching the conducting wire W by the tip of the hook 53 and the operation of releasing the conducting wire W from the tip of the hook 53 by turning the hook 53 in direction A into the open position and the close position, respectively.
Accordingly, upon feeding the conducting wire W having been wound in the circumferential guide groove 56 of the coil bobbin 51 in one of slits 58 formed by a plurality of ribs 57, it is required to ensure an operational space S for turning the hook 53 into the open position.
To be more specific, the conducting wire W is released from the hook 53 at a position P2 offset from a position P1, at which the conducting wire W is to be finally placed, by an amount equivalent to the operational space S in the direction from inside to outside of the coil bobbin 51.
Accordingly, the movement of the conducting wire W is not restricted in a distance L between the position P1 at which the conducting wire W is to be finally placed and the position P2 at which the conducting wire W is released from the hook 53.
As a result, after the winding of the conducting wire W is completed, as shown in FIG. 3, there occur variations in winding position between the conducting wire W portions wound in each slit 58 in the circumferential guide groove 56. This makes it very difficult to increase the accuracy of a winding distribution of the deflection coil.
On the other hand, the winding of the conducting wire W on the coil bobbin 51 can be performed only by operation of the nozzle 52 without use of the above-described hook 53; however, in this case, the coil bobbin 51 itself must have the function of guiding the conducting wire W.
As a result, the force applied to each rib 57 formed on the coil bobbin 51 becomes larger.
In particular, upon feeding the conducting wire W to each slit 58, as shown in FIG. 4, the conducting wire W withdrawn on the inner peripheral side of the coil bobbin by the nozzle 52 is brought into contact with the tip of the corresponding rib 57, to apply a large moment load on the contact portion (tip of the rib 57).
As a result, during the winding operation, there may occur the inconvenience that the rib 57 will be broken.
To cope with such an inconvenience, if the wall thickness of each rib 57 is made larger to increase the mechanical strength of the rib 57, the width of the slit 58 becomes narrower, to limit the winding position of the conducting wire W in the slit 58, thereby making it impossible to adjust finely the winding distribution.
Further, in the winding method making use of only the nozzle 52, the winding of the conducting wire W in the circumferential guide groove 56 of the coil bobbin 51 is performed in such a manner that a conducting wire W portion is stacked on the conducting wire W portion previously wound.
Accordingly, after the conducting wire W portions are stacked to some extent in the diameter direction of the coil bobbin 51, there may occur a phenomenon, called xe2x80x9cdisintegration of windingxe2x80x9d, in which when the next conducting wire W portion is wound, the stack of the conducting wire W portions previously wound is disintegrated.
As a result, like the winding method using the hook 53, after the winding of the conducting wire W is completed, there occur variations in winding position between the conducting wire W portions wound in each slit.
An object of the present invention is to provide a coil winding machine capable of increasing the accuracy of the winding distribution of a deflection coil and a method of producing a deflection coil by using the coil winding machine.
To achieve the above object, according to a first aspect of the present invention, there is provided a coil winding machine including: bobbin holding means for holding a coil bobbin having at each end portion a circumferential guide groove; a nozzle for feeding out a conducting wire for a deflection coil, the nozzle being movable along the inner peripheral surface of the coil bobbin in the center axis direction of the coil bobbin held by the bobbin holding means; and a winding guide having a tip portion movable in and out of the circumferential guide groove of the coil bobbin, the tip portion having a stepped portion capable of being engaged/disengaged with/from the conducting wire due to the relative positional relationship between the stepped portion and the nozzle in the center axial direction of the coil bobbin and a guide portion for restricting the feeding position of the conducting wire released from the stepped portion.
In the winding machine having the above configuration, a conducting wire fed out of the nozzle is engaged with the stepped portion of the winding guide and simultaneously the conducting wire is wound in the circumferential guide groove of a coil bobbin. The tip portion of the winding guide is then advanced in the circumferential guide groove of the coil bobbin, and the tip portion of the winding guide faces to a position at which the conducting wire is to be finally placed.
By moving, in such a state, the nozzle from one end to the other end of the coil bobbin in the center axis thereof, the relative positional relationship between the winding guide and the nozzle in the center axis direction of the coil bobbin is inverted, and thereby a drawing force is applied obliquely downward to the conducting wire engaged with the stepped portion of the winding guide.
The conducting wire is thus automatically released from the stepped portion of the winding guide, and, accordingly, upon advance of the tip portion of the winding guide in the circumferential guide groove of the coil bobbin, it is not required to ensure an operational space for releasing the conducting wire.
The conducting wire thus released from the stepped portion of the winding guide can be fed to the position at which the conducting wire is to be finally placed by guiding the conducting wire by the guide portion provided on the tip portion of the winding guide.
According to a second aspect of the present invention, there is provided a method of producing a deflection coil by using a coil winding machine, the coil winding machine including bobbin holding means for holding a coil bobbin having at each end portion a circumferential guide groove, a nozzle for feeding out a conducting wire for a deflection coil, the nozzle being movable along the inner peripheral surface of the coil bobbin in the center axis direction of the coil bobbin held by the bobbin holding means, and a winding guide having a tip portion movable in and out of the circumferential guide groove of the coil bobbin, the tip portion having a stepped portion capable of being engaged/disengaged with/from the conducting wire due to the relative positional relationship between the stepped portion and the nozzle in the center axial direction of the coil bobbin and a guide portion for restricting the feeding position of the conducting wire released from the stepped portion, and the method including the steps of engaging the conducting wire fed out of the nozzle with the stepped portion of the winding guide and simultaneously winding the conducting wire in the circumferential guide groove of the coil bobbin, and releasing the conducting wire from the stepped portion of the winding guide by moving the tip portion of the winding guide in the circumferential guide groove of the coil bobbin and moving the nozzle from one end to the other end of the coil bobbin in the center axis direction of the coil bobbin.
With this configuration, it is possible to feed the conducting wire released from the stepped portion of the winding guide up to the position at which the conducting wire is to be finally placed by guiding the conducting wire by the guide portion provided on the tip portion of the winding guide.
Accordingly, it is possible to prevent the occurrence of disintegration of the winding of the conducting wire and hence to produce a deflection coil with a high accuracy.